1. Field of the Invention
The field of art to which this invention pertains is power supply overload protection circuits and in particular to such protection circuits for protecting a power supply in the presence of transient as well as permanent overloads.
2. Description of the Prior Art
Several techniques for providing protection circuits for solid state power supplies are known in the art. These systems generally employ a fuse or other shut-down devices such as a silicon controlled rectifier, to turn off the power supply in the event of an overload. Other systems employ circuitry that shut-down the power supply when an overload is present but allow the power supply to cycle between on and off states until the overload is removed.
Although these techniques provide a degree of power supply protection, the first technique shuts-down the power supply permanently even in the event of a transient overload and requires manual resetting. The second technique provides automatic turn-on of the power supply following removal of the overload but does not provide adequate protection to the power supply when a continuing overload is present due to the fact that continuing recycling means between on and off conditions can damage the circuit and especially the output transistor.